How to delete an element from map — JavaScript
In this article we will learn how to delete an element from map.
It is very common to delete an element from map in JavaScript.
Problem
Now we have a problem, which is that we want to delete an element from the map.
Now let’s define a map like this:
// Map
const map = new Map([
['name', 'John'],
['age', 30],
]);
console.log(map);
// Map(2) { 'name' => 'John', 'age' => 30 }And we only want to delete an element from our map, so the output becomes like this:
Map(1) { 'age' => 30 }If we deleted name element
How to solve this problem?
Fortunately, there is already a function in the map that deletes items call delete(), all you have to do is use the delete() function, and pass the item you want to delete.
Delete an element using delete method
As we said before you can use delete() method to remove an element from map.
Example
// Map
const map = new Map([
['name', 'John'],
['age', 30]
]);
// Print before deleting
console.log(map);
// Delete element
map.delete('name');
// Print after deleting
console.log(map);Output
Map(2) { 'name' => 'John', 'age' => 30 }
Map(1) { 'age' => 30 }Well, now what if I want to delete the first element and I don’t know its key! What do I do?
Delete the first element of map
Now I will answer the previous question, if you want to delete the first element and you don’t know its key.
You can use Array.from() to get all the element in an array and then you can get first element easily.
// Map
const map = new Map([
['name', 'John'],
['age', 30]
]);
// Array with elements
const array = Array.from(map);
// First element
const firstEle = array[0];
// Print
console.log(firstEle);Now that we get the first element, we can delete it using delete.
// Map
const map = new Map([
['name', 'John'],
['age', 30]
]);
// Array with elements
const array = Array.from(map);
// First element
const firstEle = array[0];
// Delete first element by his key `[0]`
map.delete(firstEle[0]);
// Print
console.log(map);Output
Map(1) { 'age' => 30 }